Process for preparing rheopectic calcium 12-hydroxy stearate grease



PROCESS FOR PREPARING RHEOPECTIC CAL- CIUM IZ-HYDROXY STEARATE GREASE John W. Nelson, Lansing, UL, assignor to Sinclair Refining Company, New York, N.Y., a corporation of Mame No Drawing. Filed July 20, 1956, Ser. No. 598,982 6 Claims. (Cl. 252-39) This invention relates to anhydrous lubricant compositions and more particularly to a method of preparing lubricants containing calcium 12-hydroxy stearate.

Automation in passenger car operation is being ap plied to chassis lubrication by means of an automatic or push-button lubrication system which enables a driver to lubricate the vehicle at frequent intervals in order to pro vide a protective film of fresh lubricant on chassis components, such as tie rods, king pins and spring shackles. However, much difficulty has been experienced in the preparation of superior greases suitable for use in automatic lubrication systems since the selection of a lubricant has been limited by the choice of dispensing pumps and the flow properties or pumpability of the particular lubricant employed. For example, oils feed Well under small force, the flow increasing in proportion to the force applied, but have a tendency to drip from bearings under the influence of gravity. On the other hand, chassis greases, which do not drip under the force of gravity, feed poorly into small pump openings and require more force to initiate flow. Thus, for a lubricant to overcome these difliculties it must have how properties like oil and acquire the consistency of a grease.

In accordance with the present invention 1 have discovered that substantially anhydrous calcium lubricant compositions can be prepared which have particular utility in automatic chassis lubricator systems. The lubricant compositions of this invention are termed rheopectic greases, i.e. those which have flow properties of oil and which acquire the consistency of grease, and consist essentially of a mineral lubricating oil containing calcium 12-hydroxy stearate which constitutes about 2 to 6% by weight of the final composition. These lubricants can be obtained by subjecting dehydrated calcium greases which have a soap concentration of about 16 to 20% by weight to a post-dehydration heat treatment at temperatures between about 285 and 295 F. Although the chemical or physical changes efiected in the grease by the heat treatment are not fully understood, a definite and unexpected change occurs therein occmioned by the amount of soap employed. When the soap content is reduced and dispersed within the heat treated greases, as by homogenizing or milling to a defined consistency for example, the stabilized lubricants thus obtained are highly suitable for use in automatic lubricating systems. When subjected to shearing stress, as by pumping, thelubricant solidifies upon flow acquiring the consistency of a chassis grease and exhibits no definitive viscosity at 210 F. The compositions are further characterized as being substantially anhydrous lubricants containing less than 0.3 weight percent water.

Suitable mineral oil fractions used in preparing the lubricants of the present invention include mineral oils of wide viscosity ranges, the ranges varying from about 100 to 1000 SUS at 100 F. The preferred mineral oils have a viscosity of about 200 to 400 SUS at 100 F. and are solvent-refined oils of high viscosity index, e. g., at least about 80 and preferably at least 95. Synthetic lubricating United States-Patent O 2,940,931 Patented June 14, 1960 iceoils of the above viscosities also can be substituted in part or whole for the mineral oil. Among the synthetic oils which can beemployed are polymerized olefins, alkylated aromatics, silicone polymers, polyalkylene glycols and their partial or complete ethers and esters. It is essential in the preparation of the lubricants that the base oil employed be pour depressed, for instance, to at least about -25 F. and preferably to a range of about -25 to -35 F. The oils can be pour depresed by means of conventional pour point depressants which are normally used in amounts of about 0.1 to 5 weight percent based on the total weight of the mineral oil. A commercial material of this type used in the present invention is a methacrylate copolymer having a molecular weight of about 10,000 to 20,000 sold under the trade 'name Acryloid 710. Ordinarily, the methacrylate copolymer is employed with the mineral oil in a proportion of about 1% by weight to effect a pour point of from about -25 to --35 F.

The grease-forming or thickening material used in the present invention is calcium 12-hydroxy stearate. The calcium can be used in any of the compound forms normally employed in calcium grease manufacture, such as the inorganic oxid or hydroxide, etc., and as an example, may be present in amounts ranging from about the stoichiometric amount to a 10% excess. The soap may be added to the oil in a preformed state, or preferably, be provided by saponification in si In one method of carrying out the preparation of the lubricant compositions of this invention, a heterogeneous mixture comprising 12-hydroxy stearic acid, lime, water and oil is formed at low temperatures of about 70 to F. The oil to fatty acid ratio is generally about 2-4 to 1 parts by weight, and is preferably in a ratio of about 3 to 1 parts by Weight. Water is usually employed within a ratio of up to about 1:1 parts by weight per part of fatty acid. By employing water in the defined quantities, initiation of the saponification reaction at low temperatures is facilitated and the greases produced are characterized by water stability. Heat is applied to'the mixture and the temperature is slowly raised to F. during which time thickening occurs and the reaction proceeds to conipletion as indicated by a color change in the free Water from cloudy to clear. Free water is evaporated and the mixture is then dehydrated at temperatures below about 260 F., preferably at about ,240 to 255 F.

,until substantially complete dehydration is obtained as indicated by a Water content of less than about 0.3 weight percent. After dehydration is complete the resulting mass is subjected to the post-hydration heat treatment. This is accomplished by raising the temperature slowly to a range of about 285 to 295 F. The temperature is raised slowly to avoid localized excessive temperatures and higher temperatures above the order of 300 F. are avoided in order to prevent soap separation. During the heat treatment the water content of the grease should not exceed about 0.3 weight percent since any significant amount of water at elevated temperatures would cause the grease to become grainy.

During the heat treatment the soap concentration of the grease constitutes about 16 to 20% by weight of the total composition and it is critical that such concentration be maintained since the high concentration of the soap atfords the required amount of thickening agent necessary to achieve a given penetration. Thus, the high soap concentration present during the heat treatment is necessary to obtain greases having a minimum yield and a high penetration. The post-dehydration heat treatment is carried out for about one hour or more, or until such time asthe entire mass appears soft with a flat surface, thus indicating that the grease has a minimum yield and fluid characteristics. Before the heat treatment; it may be n ecesary to add an amount of base oil pared substantially as in v[tof adjust the soap concentration to thatrequired. Before or after dehydration;the composition can contain upwards ofabo'ut l6%"soap based on-the oil and soap, e.g. about 116..to 5 %,.or more, preferably about 16 to'*35%,*

' would be made Following the heat treatmentiadditiona'l 'pour depressed oil" is added to the'mass in an amount and also. prevents soap 'separation' after standing several m ma 7 Infthe following example whichiillustrates one method of prepaiingmyirheopectic lu ricants, IZ-hydreXystearie acid is saponi fiedin situ and is then dehydrated prior to "It is to be underthe pos tejdehydration heat tr'eatrnen stood, however, that. :theLheaL treatment can'be applied directlytci greases inwhich the required amount of soap .hasbeenadded to oil in aprcfornied state, assuming, of course, that the soapihas:been' dispersed andthat the oil contains less'i-than about 5% Water.

" EXAMPLE I l6 po unds of l2 -h'ydroxy stearic acid, -l6jpounds of Waterand-233 pounds'lime slurriedQin 48 pounds ofian 1 oil blend were charged into a 400 pound capacity grease kettle. The oil blend had a viscosity of 303 SUS at 100 and consisted'of amixture of solvent-refined Mid Continent neutral oils comprising.68.8 Weight percent of,

'QS VI oil .having'a viscosity off3 2ilSUS-at100f-F. and

ii and -if the;"amount'is 'above'ab'out20%, an adjustment Example I were tested for .pumpability characteristics. The test apparatus was de-. signed to simulate automatic'chassis lubrication systems employed in passenger cars. Generally, these systems consist. of a vacuum diaphragm operated pump, lubricant reservoir, and flexible lubricant supply lines running from the pump to each chassis lubrication point. This assembly is mounted in the engine compartment and is connected to a push-button control and indicator light .on the instrument panel. Pushing the control button pumps the grease through the feed lines and as soon'as [the last fitting has been lubricated, the indicator light goes on, the control button is released and the pump recharges'for the next lubricating cycle. 1

The data in Table I were obtained by placing the automatic lubricating test apparatus in a refrigerated bOX with the control button and indicator light mounted outside the box. A laboratory vacuum pump and appropriate valving were used to simulate passenger car 31.2 weight. percent of a' 95 Vi oil havinga viscosity of xiZOQSUS at 109" F; One percent Acryloid 71 0based on the Weight of oilrwa's added to efiect 'a pour point of .-25 Thekettle contents were stirred cold for 1-0 minutes :and'then heated to about 160 F. Heatingw'as discontinuedtorclllminutes and then reapplied. While the temperature Waslincreasing. to 260 F free water-and .a heavy soapfemulsionwere evident. 7 l ljter, about one h u'rZthe'iree Waterhad disappeared andLthesoap-oil mixture. appeared smooth and flat; Twenty-feur'pounds of oil then iverea'dded toprovidea soa'p concentration of 1 18.2 percentby weight. 'The "temperaturewasimaini tained at about 255 F. for. about one hour during: Which-i dehydration "occurred. {The time essentially complete "temperature, then Was incre' 7 ithefgr'ease. consistency changed from hardito very soft; This procedurerequiredabout '2. hours. The heat Was turned olf and 23 2 pounds'of bilwere added to provide asedslowlyito- 2925's. and r a soap concentration of 5%. The fluid mass was cooled to 120 F a ndmilled at .O20"Iclearance in a Charlotte colloid mill. The lubricant hadthe following character.-

i'stics;

SlL Mobilometer, 40 gram load 31 seconds. Free alkali, percentCaO j 0.104. Percent Water Trace.

Multi luher, l\}

As previously imentionedy adequate performance of lubricantsfor automatic lubrlcator'systernsdepends to a greater; at upcn the lubricant flow properties or.pumpa bility characteristics. This is particularly importantat lower temperatures, forexample; 265E. to;1'0 R, where viscosity or how characteristics can change radii cally and thusresult in no lubrication. To demonstrate the advantages'obtained by this inrentiom' several com- F. cycle test Excellent.

mercial automatic lubri cator greases and a lubricantpre 4 Tablel LUBRICANT PUMPABILITYTESTS Sample i A k ,3 Identity Commercial Soap Typo 'Al Ca Soap Content, Percent" 4. 9 x 5.0 Pour Point, E T20 '5 Milled 1 Yes SIL Mobilometer, sees; (40. gm. 36 J Viscosity of Oil, SUS 100 F--- f 429' 300 Vacuum inches hg.

'b icant Tem erature, F.': r i2 w p r 22 1.? 1.6 18 2. O V 1. 9 14 2. 4 2. 4 10 3. 8, 4. 7 '22 2.5 r 1.9 18 s. 1 2. 2 14. 4. 0 3.0 10 7. 1 v 6. 7 22 7.0 4.1 .18 8. 8 5.8 14 15. 8 8. 9 22 51; l 25. 4 18 100. 5 49.4

operation. I A vacuum range'of 14 to 22.inches of met.- cury covered idling"conditionsof current passenger .car engines. .Lubricant pumpability ratings'were based on the time required to complete a lubrication cycle at a given lubricant temperature and simulated engine vacuum condition under" free-flow pumping conditions. Eleven grease fittings were in the automatic lubricator unit. 7 f

The lubricant prepared substantially as in Example I had the following characteristics:

Pour point, F rnax. 5 SIL'Mobilometer 40 gram load seconds 15-35 'Watcr, percent max j i 0.1

'Free alkali, percent CaO 0.2

Asshown in Table I the calcium soap-base lubricants preparedin accordance with this invention show superior low temperature'pumpability characteristics when com pared ,to a commercial aluminum-base lubricant iofthe 7 type employed inautomatic lubr'icator systems] At temperatures of .10 underavacuum range of 14 to 22 inches of mercury, the pumping cycle of sample B aver,- aged less than 50% 'of'the time required for the commercial sam'pleA. T i v Charlotte colloid Mill (0.020" 0.0?O clearance)? F. p

Erraticoperation; g V" V V I claim:

1. In a method for preparing a substantially: -anhy drous calcium lubricant composition, the stepsqwhi ch comprise forming calcium l2-hydroxy stearate soap.1n

the presence of Water andja pour depressed lubricating oil to provide a mixture having a soap concentration of from about 16 to 20% by weight based on the soap and oil, dehydrating said mixture at a temperature below about 260 F. to efiect substantially complete dehydration, heating the dehydrated mixture at a temperature of from about 285 to 295 F. until such time 'as the entire mass is soft with a flat surface, adding pour depressed lubricating oil to said composition to afford a soap concentration of from about 2 to 6% by weight, and thereafter dispersing said soap to obtain a lubricant having a consistency of from about 10 to 50 seconds in an SIL Mobilometer using a 40 gram Weight.

2. The method of claim 1 in which said lubricating oil is a mineral oil having a viscosity of from about 200 to 400 S U-S at 100 F. and a viscosity index of at least about 95.

3. The method of claim 2 in which said lubricating oil is pour depressed within a range of from about 25 to 35 F.

4. The method of claim 3 in which said soap is dispersed by means of a colloid mill.

5. In a method for preparing a substantially anhydrous calcium lubricant composition, the steps which comprise forming a substantially anhydrous mixture of a pour depressed lubricating oil and about 16 to 20% by weight of calcium 12-hydroxy stearate soap, heating the mixture at a temperature between about 285 to 295 F. until such time as the entire mass is soft with a fiat surface, adding pour depressed lubricating oil to said composition to afford a soap concentration of from about 2 to 6% by Weight, and thereafter dispersing said soap to obtain a lubricant having a consistency of from about 10 to 50 seconds in an SIL Mobilometer using a 40 gram weight. w

6. The method of claim 5 in which said lubricating oil is pour depressed to about to F.

References Cited in the file of this patent UNITED STATES PATENTS 2,312,725 Morway et al. Mar. 2, 1943 2,607,734 Sproule et al. Aug. 19, 1952 2,607,735 Sproule et al. Aug. 19, 1952 OTHER REFERENCES The Manufacture and Application of Lubricating Greases, Boner, Reinhold Pub. Corp., N.Y., 1954, pp. 117 and 118. 

1. IN A METHOD FOR PREPARING A SUBSTANTIALLY ANHYDROUS CALCIUM LUBRICANT COMPOSITION, THE STEPS WHICH COMPRISE FORMING CALCIUM 12-HYDROXY STEARATE SOAP IN THE PRESENCE OF WATER AND POUR DEPRESSED LUBRICATING OIL TO PROVIDE A MIXTURE HAVING A SOAP CONCENTRATION OF FROM ABOUT 16 TO 20% BY WEIGHT BASED ON THE SOAP AND OIL, DEHYDRATING SAID MIXTURE AT A TEMPERATURE BELOW ABOUT 260*F. TO EFFECT SUBSTANTIALLY COMPLETE DEHYDRATION, HEATING THE DEHYDRATED MIXTURE AT A TEMPERATURE OF FROM ABOUT 285 TO 295*F. UNTIL SUCH TIME AS THE ENTIRE MASS IS SOFT WITH A FLAT SURFACE, ADDING POUR DEPRESSED LUBRICATING OIL TO SAID COMPOSITION TO AFFORD A SOAP CONCENTRATION OF FROM ABOUT 2 TO 6% BY WEIGHT AND THEREAFTER DISPERSING SAID SOAP TO OBTAIN A LUBRICANT HAVING A CONSISTENCY OF FROM ABOUT 10 TO 50 SECONDS IN AN SIL MOBILOMETER USING A 40 GRAM WEIGHT. 